The present invention relates generally to a musical instrument capable of producing or generating an additional vibration sound and a method for adding an additional vibration sound in a musical instrument, and more particularly the present invention relates to a technique for generating an additional vibration sound using a vibrator (electric-to-vibration transducer) to impart mechanical vibration to the body of a musical instrument (such as an acoustic guitar) and thereby generate an additional vibration sound.
A technique has heretofore been known according to which a voice-coil type actuator (speaker) is mounted to the soundboard of a piano, and physical vibration of the actuator is transmitted to the soundboard so that a mechanical vibration sound is generated from the soundboard (see, for example, Patent Literatures 1 and 2 identified below). Further, according to this conventionally-known technique, a sound source of an electric waveform signal to be supplied to the actuator is an electronic sound source, not a live sound played or performed on a piano. Namely, this conventionally-known technique is arranged in such a manner that turning-on of any one of the keys of the piano is detected, an electric waveform signal having a pitch corresponding to the turned-on key is generated from the electronic sound source and then the actuator is driven by the electric waveform signal. Thus, with this conventionally-known technique, there is no need to take into consideration problems of howling etc. caused by a live performed sound being fed back to a loop of the mechanical vibration sound generated by the actuator.
Further, Patent Literature 3 identified below discloses electrically picking up string vibration in a stringed instrument, such as a guitar, amplifying the picked-up string vibration signal, and then causing a mechanical vibration sound to be generated from the body of the musical instrument by driving an actuator with the string vibration signal. However, with the technique disclosed in Patent Literature 3, a problem of howling would occur by the string vibration signal, generated by a performance of the stringed instrument, being fed back to a loop of the mechanical vibration sound generated by the actuator. The technique disclosed in Patent Literature 3 does not at all take such a howling problem into consideration. Patent literature 3 also discloses performing signal processing on the picked-up string vibration signal for varying the musical interval (or pitch) of the string vibration signal and then driving the actuator with the thus-processed electric vibration signal so that a mechanical vibration sound with controlled tonality is generated from the body of the musical instrument. However, because the signal processing disclosed in Patent Literature 3 is designed primarily to cause a sound of different tonality (musical interval or pitch) from the string vibration sound to be generated through vibration of the body of the instrument, there is no need to take the problem of howling into consideration, and thus, Patent Literature 3 does not at all teach a solution to the howling.
Furthermore, ceramic speakers have been known as compact vibrator devices, and it has been known to mount such a ceramic speaker on a hard object or body and generate a vibration sound by vibrating the hard body (see, for example, Non-patent Literature 1 identified below). As far as the Applicant knows, there has been no precedent example where such a ceramic speaker is used as a mechanical vibration source for a musical instrument. However, considering the prior techniques as disclosed in Patent Literatures 1 and 2 that are applied to a piano, the compact vibrator devices, such as the ceramic speakers, are deemed to be suitable for use in a relatively small-sized musical instrument like a guitar. What is more, Patent Literature 4 identified below discloses a game device where a first sound signal having been subjected to effect processing and a second sound signal having not been subjected to effect processing are generated and sounded in parallel, on the basis of same sound data, to enhance an acoustic effect. However, Patent Literature 4 discloses nothing about applying such effect processing to addition of a mechanical vibration sound in a musical instrument.
Patent Literature 1: Japanese Patent Application Laid-open Publication No. HEI-4-500735
Patent Literature 2: International Publication No. WO2013/089239
Patent Literature 3: Japanese Patent Application Laid-open Publication No. 2003-295865
Patent Literature 4: Japanese Patent Application Laid-open Publication No. 2014-057809
Non-patent Literature 1: http://eishindenki.com/index.php?data=./data15/
However, using a dedicated electronic sound source, like that shown in Patent Literature 1 or 2, as a source of an electric waveform signal to be supplied to the vibrator device would increase the necessary cost and thus is not preferable in cases where it is intended to provide low-cost equipment. Further, there would be presented another disadvantage that subtleties of the actual performed sound of the musical instrument cannot be reflected in the mechanical vibration sound. Thus, detecting a live performed sound of a musical instrument, such as a guitar, by means of a pickup and using the thus-detected live performed sound as a source of an electric waveform signal to be supplied to a vibrator device is advantageous not only in terms of the necessary cost but also for the purpose of allowing the subtleties of the actual performed sound of the musical instrument to be reflected in the mechanical vibration sound. However, if such an approach is employed, there would occur problems, such as howling, caused by the performed sound of the musical instrument being fed back to a loop of the mechanical vibration sound generated by the vibrator device.